1. Field of the Invention
The present invention relates to a fixing apparatus, an image forming system employing the fixing apparatus, and a method of controlling power sources to supply power to the fixing apparatus.
2. Discussion of the Background Art
It is known that a power stored in a secondary battery is supplied to an auxiliary heater of a fixing apparatus when sheets are successively fed, as discussed in Japanese Patent Application Laid Open No. 2000-98799. It is also known that a condenser supplies power to an auxiliary heat generating member included in a heat applying apparatus when a system starts up, as discussed in Japanese Patent Application Laid Open No. 2002-184554.
These conventional apparatuses generally employ a halogen heater as a heat-generating member, because of excellent efficiency of heating and starting up quickly.
A problem is an inrush current that is generated when a fixing apparatus or the like utilizes a halogen heater and power is supplied. That is, a large current flows because a resistance of a filament included in the halogen heater is small in an ambient temperature. Specifically, a current of from dozens to a hundred and dozens of Amperes flows through a circuit in a moment. This inrush current gives adverse affect to peripheral instruments because switching parts melt and a power source voltage temporary decreases. When a typical halogen heater having about 1200 w when a commercial power source of 100V is applied is used, both a filament temperature and a resistance increase, and the inrush current is accordingly settled. Thus, a steady current starts flowing.
In order to avoid such an inrush current and resolve a problem of delayed starting up, the above-mentioned inrush current is conventionally decreased by controlling a duty cycle from dozens of hundred mili seconds to one second (i.e., executing soft ON control) in order to restrict a power when a power source is turned on. However, this method takes a long time until temperature of the filament of the halogen heater increases to a prescribed level, and accordingly, heat applied to a fixing roller by generating a light by itself from the halogen heater delays. Even such a time period of from dozens of hundred mili to one second raises a significant problem when temperature is increased within ten seconds as expected by a user.
Further, in order to reduce the inrush current flowing from the commercial power source to the halogen heater, so called “soft control” is executed to restrict a power supplied from the commercial power source when temperature starts increasing so that a rated current of the commercial power source due to the inrush current is not exceeded. However, such soft control delays the halogen heater in starting up, and accordingly delays a fixing roller as a heating objective in increasing temperature. However, a fixing apparatus for copier use is expected nowadays to quickly start up and accordingly save power consumed during warming up as environment protection increasingly receives attention. Thus, a certain technology is demanded to decrease a rated power using soft control and quickly increase temperature of the fixing roller.